How are yall running 3 phase machines in home shops?

Ben Kabisch

Ben Kabisch

Knifemaker / Craftsman / Service Provider
Joined
May 22, 2003
Messages
262
So I’ve been using a phase o matic phase converter on my surface grinder (the only 3 phase machine I have) and this is the 3rd one I’ve had to replace (they have always given me issues)…so another knifemaker told me to buy a kbac drive to run my surface grinder next time, so I did. Well time has come to replace the phase o matic again, so I went to put the KBAC27D drive on and come to find out it won’t work, apparently because of the oil pump thats inside there. The drive won’t give enough juice to turn the motor over and keep start button engaged unless I hit the start button 3 or 4 times quickly and then it will start up, but they can’t tell me if I’m gonna burn something up by doing that…so now I’ve been told I need to get a rotary phase converter. What are yall doing to run these 3 phase machines in your home shops?
 
My old neighbors dad had a machine shop at home and made one out of an old 220V electric motor. It was years ago and I don’t remember the sizes or anything but they were running a mill and lathe off of it with no issues.

A lot of folks are going the VFD route now but it sounds like you need more juice. Have you looked at other VFDs besides the KBAC? Can you wire the oil pump to a different source and start it separately?
 
first question is what are the specs of the motor in that surface grinder bc the kbac27d only does 230v 6.7amps max output on 240v input and only 5.5a on 120v

kbac29(1p) does 9a max output on 240v single phase input

if you need anymore juice than that or your motor is rated for a different voltage spec you prob gonna have to go to another drive that can support it on single phase input or you just need 3 phase outright
 
This is the motor… i can make knives but i know nothing about electricity and motors. I was told this drive would work for this motor when i purchased itIMG_2437.jpeg
 
You can just use a three phase motor as a converter. Need a way to spin it up, and it needs to be at least double the capacity of the motor it is driving. Drive it on single phase across one incoming pair, and run load from all lines. I ran off a big old surplus 15hp motor for a long time, with no balancing caps or anything. Just started it up using a smaller motor to drive it. I have instructions here somewhere on sizing balancing caps and starter caps to build your own rotary converter panel. I haven't done it.

These folks will sell you just a panel if you can find a surplus motor https://www.northamericaphaseconverters.com/phase-converters/control-panels/, or a full converter if necessary. I've never dealt with them, but have read ok things about them.

I have a proper rotary converter now, and I will say that not fussing with starting it up is nice.

Being in Canada, I bought mine from https://www.phase-quest.com/ They were ok to deal with, and the converter is working fine. (I have some big stuff I'm driving, over 7hp of load at times.)
 
A rotary phase converter probably wouldn't be the worst investment, especially if you have multiple 3 phase machines (or plan on adding more in the future), but you should be able to run your surface grinder with you existing VFD. The problem is that you're trying to run it through a magnetic starter. That's a good way to pretty quickly ruin your VFD if you're not careful.

You'll want to eliminate that magnetic starter and use the start/stop switches on your VFD instead, in order to start and stop your machine. In other words, you should be able to just wire that motor directly to the VFD and just use it's built in on/off and start/stop control switches.
 
Drew Riley said:
A rotary phase converter probably wouldn't be the worst investment, especially if you have multiple 3 phase machines (or plan on adding more in the future), but you should be able to run your surface grinder with you existing VFD. The problem is that you're trying to run it through a magnetic starter. That's a good way to pretty quickly ruin your VFD if you're not careful.

You'll want to eliminate that magnetic starter and use the start/stop switches on your VFD instead, in order to start and stop your machine. In other words, you should be able to just wire that motor directly to the VFD and just use it's built in on/off and start/stop control switches.
Click to expand...

This is the only 3 phase machine I have and don’t plan on any others…That’s what I was thinking, but If I run the vfd straight to the motor will my oil pump still work when I flip the switch on the vfd?
Thank yall for the replies!
 
I have a Harig surface grinder, the motor looks the same as yours. what I did is disconnect the motor and oil pump from the control panal on the machine, I kind of went the extra mile with mine by making this control panel with a 220 and 110 feed. The 220 goes to the vfd and the cable for the motor goes directly to it. Your oil pump should run on 110, mine did. so I have a switch on that panel to turn on the oil pump. IMG_3856.jpegIMG_3855.jpeg
 
My oil pump is a 230v, just found my wiring diagram… think I’m just gonna bite the bullet and get a rotary phase converter and hope it lasts longer than those static ones I’ve been using!
 
Ben Kabisch said:
So I’ve been using a phase o matic phase converter on my surface grinder (the only 3 phase machine I have) and this is the 3rd one I’ve had to replace (they have always given me issues)…so another knifemaker told me to buy a kbac drive to run my surface grinder next time, so I did. Well time has come to replace the phase o matic again, so I went to put the KBAC27D drive on and come to find out it won’t work, apparently because of the oil pump thats inside there. The drive won’t give enough juice to turn the motor over and keep start button engaged unless I hit the start button 3 or 4 times quickly and then it will start up, but they can’t tell me if I’m gonna burn something up by doing that…so now I’ve been told I need to get a rotary phase converter. What are yall doing to run these 3 phase machines in your home shops?
Click to expand...
 
The reason your Phase-O-Matics kept dying is they're static converters — basically a bank of capacitors trying to fake a third phase. They work okay for simple single-motor loads, but a surface grinder with a hydraulic oil pump is asking a lot. The capacitors degrade over time, especially with the inrush from that oil pump cycling.

The KBAC drive issue makes total sense too. A VFD is a single-motor device — it wants to control one motor directly. Your surface grinder has at least two motors (spindle + oil pump), and the VFD can't manage both. That's why it chokes on startup. Hitting the start button multiple times is basically brute-forcing past the inrush, and yeah, I wouldn't keep doing that — you'll eventually cook something.

A rotary phase converter is the right answer here. It generates true, balanced three-phase power — same quality as what the utility would deliver. You wire it to a small sub-panel, and everything downstream runs exactly how the manufacturer designed it. Spindle motor, oil pump, magnetic starter, all of it. No programming, no parameters, just flip the switch.

For sizing, the general rule is 2x your largest motor HP. So if your grinder has a 2HP spindle, a 5HP converter handles it with plenty of headroom. If you ever add another three-phase machine (heat treat oven, belt grinder, etc.), it's already powered.

Full disclosure — I'm Glen from Phoenix Phase Converters. We've been building these for over 50 years, made in the USA, lifetime warranty. But honestly, any quality rotary converter will solve this permanently. The technology is dead simple and they last decades. Happy to help you size it if you want to share your grinder model .
 
Last edited by a moderator:
Moderator -
Thanks Glen for a simple explanation of the issue.

Normally, your thread would be blocked and your account banned for SPAM. Since you only offered a good explanation and help, I'm leaving it up. A super-mod may still take a different action, but for the time being, it will stay as help for the OP and others. I did remove your phone number, because that would be advertisement.
 
Phoenix Phase Converters said:
The reason your Phase-O-Matics kept dying is they're static converters — basically a bank of capacitors trying to fake a third phase. They work okay for simple single-motor loads, but a surface grinder with a hydraulic oil pump is asking a lot. The capacitors degrade over time, especially with the inrush from that oil pump cycling.

The KBAC drive issue makes total sense too. A VFD is a single-motor device — it wants to control one motor directly. Your surface grinder has at least two motors (spindle + oil pump), and the VFD can't manage both. That's why it chokes on startup. Hitting the start button multiple times is basically brute-forcing past the inrush, and yeah, I wouldn't keep doing that — you'll eventually cook something.

A rotary phase converter is the right answer here. It generates true, balanced three-phase power — same quality as what the utility would deliver. You wire it to a small sub-panel, and everything downstream runs exactly how the manufacturer designed it. Spindle motor, oil pump, magnetic starter, all of it. No programming, no parameters, just flip the switch.

For sizing, the general rule is 2x your largest motor HP. So if your grinder has a 2HP spindle, a 5HP converter handles it with plenty of headroom. If you ever add another three-phase machine (heat treat oven, belt grinder, etc.), it's already powered.

Full disclosure — I'm Glen from Phoenix Phase Converters. We've been building these for over 50 years, made in the USA, lifetime warranty. But honestly, any quality rotary converter will solve this permanently. The technology is dead simple and they last decades. Happy to help you size it if you want to share your grinder model .
Click to expand...

Thank you for the explanation! I ended up purchasing a 5hp rotary phase converter and installed it this past weekend and everything is working great now!
 
That tip on the wild leg is spot on!

Just to add one more piece of setup advice: since you went with a rotary converter, you are probably noticing that the idler motor whines pretty loudly. A lot of home shop guys eventually build a small, insulated "doghouse" enclosure outside to hold the converter, and then just pipe the conduit through the wall to save their hearing.

If you end up building an exterior shed for it, take the time to properly slope, shingle, and flash the roof. In my day job at best roofing in west palm beach, I can't tell you how many expensive outdoor electrical components (pool pumps, compressors, and converters) I've seen get completely fried because someone just slapped a flat piece of raw plywood over a makeshift shed. Put a proper drip edge and membrane on it so your new investment stays totally dry.

Congrats on getting the surface grinder running!
 
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